21989871 has 12 divisors (see below), whose sum is σ = 31941000. Its totient is φ = 14577840.

The previous prime is 21989861. The next prime is 21989873. The reversal of 21989871 is 17898912.

It is not a de Polignac number, because 21989871 - 2⁵ = 21989839 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21989873) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5121 + ... + 8378.

It is an arithmetic number, because the mean of its divisors is an integer number (2661750).

Almost surely, 2^21989871 is an apocalyptic number.

21989871 is a deficient number, since it is larger than the sum of its proper divisors (9951129).

21989871 is a wasteful number, since it uses less digits than its factorization.

21989871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13686 (or 13683 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 21989871 is about 4689.3358804846. The cubic root of 21989871 is about 280.1609236515.

The spelling of 21989871 in words is "twenty-one million, nine hundred eighty-nine thousand, eight hundred seventy-one".